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Merged
harsimar merged 3 commits into from
Mar 24, 2026
Merged

Change gen-ai attribute truncation from exempt to 256KB limit #57194

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854778f
Initial plan
Copilot Mar 17, 2026
41ae456
Change gen-ai attributes truncation from exempt to 256KB limit
Copilot Mar 17, 2026
7989f4f
chore: trigger CI re-evaluation
harsimar Mar 23, 2026
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14 changes: 8 additions & 6 deletions sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,9 +49,10 @@ internal static class LogsHelper
{
if (!properties.ContainsKey(scopeItem.Key))
{
var stringValue = SchemaConstants.TruncationExemptProperties.Contains(scopeItem.Key)
? Convert.ToString(scopeItem.Value, CultureInfo.InvariantCulture)!
: Convert.ToString(scopeItem.Value, CultureInfo.InvariantCulture)?.Truncate(SchemaConstants.MessageData_Properties_MaxValueLength)!;
var maxValueLength = SchemaConstants.GenAiProperties.Contains(scopeItem.Key)
? SchemaConstants.GenAi_Properties_MaxValueLength
: SchemaConstants.MessageData_Properties_MaxValueLength;
var stringValue = Convert.ToString(scopeItem.Value, CultureInfo.InvariantCulture)?.Truncate(maxValueLength)!;
properties.Add(scopeItem.Key, stringValue);
}
}
Expand Down Expand Up @@ -190,9 +191,10 @@ internal static void ProcessLogRecordProperties(LogRecord logRecord, IDictionary
{
if (!properties.ContainsKey(item.Key))
{
var stringValue = SchemaConstants.TruncationExemptProperties.Contains(item.Key)
? item.Value.ToString()!
: item.Value.ToString().Truncate(SchemaConstants.MessageData_Properties_MaxValueLength)!;
var maxValueLength = SchemaConstants.GenAiProperties.Contains(item.Key)
? SchemaConstants.GenAi_Properties_MaxValueLength
: SchemaConstants.MessageData_Properties_MaxValueLength;
var stringValue = item.Value.ToString().Truncate(maxValueLength)!;
properties.Add(item.Key, stringValue);
}
}
Expand Down
11 changes: 8 additions & 3 deletions sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/SchemaConstants.cs
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Expand Up @@ -129,11 +129,16 @@ internal static class SchemaConstants
public const int Tags_AiInternalSdkVersion_MaxLength = 64;

/// <summary>
/// GenAI semantic convention property keys that are exempt from value truncation.
/// Maximum value length for GenAI semantic convention properties (256 KB).
/// These properties may carry large payloads (e.g. full prompt/completion content)
/// and must not be truncated.
/// and are truncated to a higher limit than standard properties.
/// </summary>
public static readonly HashSet<string> TruncationExemptProperties = new HashSet<string>(StringComparer.Ordinal)
public const int GenAi_Properties_MaxValueLength = 256 * 1024;
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harsimar marked this conversation as resolved.

/// <summary>
/// GenAI semantic convention property keys that receive a higher truncation limit.
/// </summary>
public static readonly HashSet<string> GenAiProperties = new HashSet<string>(StringComparer.Ordinal)
{
"gen_ai.input.messages",
"gen_ai.output.messages",
Expand Down
14 changes: 8 additions & 6 deletions sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/TraceHelper.cs
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Expand Up @@ -109,9 +109,10 @@ internal static void AddKvpToDictionary(IDictionary<string, string> destination,
{
// Note: if Key exceeds MaxLength or if Value is null, the entire KVP will be dropped.
// In case of duplicate keys, only the first occurence will be exported.
var stringValue = SchemaConstants.TruncationExemptProperties.Contains(keyValuePair.Key)
? Convert.ToString(keyValuePair.Value, CultureInfo.InvariantCulture) ?? "null"
: Convert.ToString(keyValuePair.Value, CultureInfo.InvariantCulture).Truncate(SchemaConstants.KVP_MaxValueLength) ?? "null";
var maxValueLength = SchemaConstants.GenAiProperties.Contains(keyValuePair.Key)
? SchemaConstants.GenAi_Properties_MaxValueLength
: SchemaConstants.KVP_MaxValueLength;
var stringValue = Convert.ToString(keyValuePair.Value, CultureInfo.InvariantCulture).Truncate(maxValueLength) ?? "null";
#if NET
destination.TryAdd(keyValuePair.Key, stringValue);
#else
Expand All @@ -130,9 +131,10 @@ internal static void AddKvpToDictionary(IDictionary<string, string> destination,
{
// Note: if Key exceeds MaxLength or if Value is null, the entire KVP will be dropped.
// In case of duplicate keys, only the first occurence will be exported.
var sanitizedValue = SchemaConstants.TruncationExemptProperties.Contains(key)
? value
: value.Truncate(SchemaConstants.KVP_MaxValueLength) ?? "null";
var maxValueLength = SchemaConstants.GenAiProperties.Contains(key)
? SchemaConstants.GenAi_Properties_MaxValueLength
: SchemaConstants.KVP_MaxValueLength;
var sanitizedValue = value.Truncate(maxValueLength) ?? "null";
#if NET
destination.TryAdd(key, sanitizedValue);
#else
Expand Down
46 changes: 22 additions & 24 deletions ...er.Tests/GenAiTruncationExemptionTests.cs → ...ry.Exporter.Tests/GenAiTruncationTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,13 +17,16 @@

namespace Azure.Monitor.OpenTelemetry.Exporter.Tests
{
public class GenAiTruncationExemptionTests
public class GenAiTruncationTests
{
private const int LargePayloadLength = 64_000;
/// <summary>
/// A payload larger than the 256 KB GenAI truncation limit to verify truncation occurs.
/// </summary>
private const int LargePayloadLength = 300_000;

private static readonly string s_largePayload = new string('x', LargePayloadLength);

static GenAiTruncationExemptionTests()
static GenAiTruncationTests()
{
Activity.DefaultIdFormat = ActivityIdFormat.W3C;
Activity.ForceDefaultIdFormat = true;
Expand All @@ -45,7 +48,7 @@ static GenAiTruncationExemptionTests()
[InlineData("gen_ai.tool.call.arguments")]
[InlineData("gen_ai.tool.call.result")]
[InlineData("gen_ai.evaluation.explanation")]
public void GenAiProperties_AreNotTruncated_InAddPropertiesToTelemetry(string propertyKey)
public void GenAiProperties_AreTruncatedTo256KB_InAddPropertiesToTelemetry(string propertyKey)
{
// Arrange
IDictionary<string, string> destination = new Dictionary<string, string>();
Expand All @@ -57,8 +60,7 @@ public void GenAiProperties_AreNotTruncated_InAddPropertiesToTelemetry(string pr

// Assert
Assert.True(destination.TryGetValue(propertyKey, out var value));
Assert.Equal(LargePayloadLength, value!.Length);
Assert.Equal(s_largePayload, value);
Assert.Equal(SchemaConstants.GenAi_Properties_MaxValueLength, value!.Length);
}

[Theory]
Expand All @@ -69,7 +71,7 @@ public void GenAiProperties_AreNotTruncated_InAddPropertiesToTelemetry(string pr
[InlineData("gen_ai.tool.call.arguments")]
[InlineData("gen_ai.tool.call.result")]
[InlineData("gen_ai.evaluation.explanation")]
public void GenAiProperties_AreNotTruncated_InAddKvpToDictionary_WithStringOverload(string propertyKey)
public void GenAiProperties_AreTruncatedTo256KB_InAddKvpToDictionary_WithStringOverload(string propertyKey)
{
// Arrange
IDictionary<string, string> destination = new Dictionary<string, string>();
Expand All @@ -79,8 +81,7 @@ public void GenAiProperties_AreNotTruncated_InAddKvpToDictionary_WithStringOverl

// Assert
Assert.True(destination.TryGetValue(propertyKey, out var value));
Assert.Equal(LargePayloadLength, value!.Length);
Assert.Equal(s_largePayload, value);
Assert.Equal(SchemaConstants.GenAi_Properties_MaxValueLength, value!.Length);
}

[Fact]
Expand Down Expand Up @@ -121,7 +122,7 @@ public void NonGenAiProperties_AreTruncated_InAddKvpToDictionary_WithStringOverl
[InlineData("gen_ai.tool.call.arguments")]
[InlineData("gen_ai.tool.call.result")]
[InlineData("gen_ai.evaluation.explanation")]
public void GenAiProperties_AreNotTruncated_InLogRecordAttributes(string propertyKey)
public void GenAiProperties_AreTruncatedTo256KB_InLogRecordAttributes(string propertyKey)
{
// Arrange
var logRecords = new List<LogRecord>();
Expand All @@ -132,10 +133,10 @@ public void GenAiProperties_AreNotTruncated_InLogRecordAttributes(string propert
options.IncludeFormattedMessage = true;
options.AddInMemoryExporter(logRecords);
});
builder.AddFilter(typeof(GenAiTruncationExemptionTests).FullName, LogLevel.Trace);
builder.AddFilter(typeof(GenAiTruncationTests).FullName, LogLevel.Trace);
});

var logger = loggerFactory.CreateLogger<GenAiTruncationExemptionTests>();
var logger = loggerFactory.CreateLogger<GenAiTruncationTests>();

// Use LoggerMessage.Define pattern to add structured attributes
var state = new List<KeyValuePair<string, object?>>
Expand All @@ -151,8 +152,7 @@ public void GenAiProperties_AreNotTruncated_InLogRecordAttributes(string propert

// Assert
Assert.True(properties.TryGetValue(propertyKey, out var value), $"Property '{propertyKey}' should exist in the properties dictionary.");
Assert.Equal(LargePayloadLength, value!.Length);
Assert.Equal(s_largePayload, value);
Assert.Equal(SchemaConstants.GenAi_Properties_MaxValueLength, value!.Length);
}

[Fact]
Expand All @@ -167,10 +167,10 @@ public void NonGenAiProperties_AreTruncated_InLogRecordAttributes()
options.IncludeFormattedMessage = true;
options.AddInMemoryExporter(logRecords);
});
builder.AddFilter(typeof(GenAiTruncationExemptionTests).FullName, LogLevel.Trace);
builder.AddFilter(typeof(GenAiTruncationTests).FullName, LogLevel.Trace);
});

var logger = loggerFactory.CreateLogger<GenAiTruncationExemptionTests>();
var logger = loggerFactory.CreateLogger<GenAiTruncationTests>();

var state = new List<KeyValuePair<string, object?>>
{
Expand All @@ -196,10 +196,10 @@ public void NonGenAiProperties_AreTruncated_InLogRecordAttributes()
[InlineData("gen_ai.tool.call.arguments")]
[InlineData("gen_ai.tool.call.result")]
[InlineData("gen_ai.evaluation.explanation")]
public void GenAiProperties_AreNotTruncated_InActivityCustomDimensions(string propertyKey)
public void GenAiProperties_AreTruncatedTo256KB_InActivityCustomDimensions(string propertyKey)
{
// Arrange
using var activitySource = new ActivitySource(nameof(GenAiTruncationExemptionTests));
using var activitySource = new ActivitySource(nameof(GenAiTruncationTests));
using var activity = activitySource.StartActivity(
"TestActivity",
ActivityKind.Client,
Expand All @@ -214,8 +214,7 @@ public void GenAiProperties_AreNotTruncated_InActivityCustomDimensions(string pr

// Assert
Assert.True(remoteDependencyData.Properties.TryGetValue(propertyKey, out var value), $"Property '{propertyKey}' should exist in dependency custom dimensions.");
Assert.Equal(LargePayloadLength, value!.Length);
Assert.Equal(s_largePayload, value);
Assert.Equal(SchemaConstants.GenAi_Properties_MaxValueLength, value!.Length);
}

[Theory]
Expand All @@ -226,10 +225,10 @@ public void GenAiProperties_AreNotTruncated_InActivityCustomDimensions(string pr
[InlineData("gen_ai.tool.call.arguments")]
[InlineData("gen_ai.tool.call.result")]
[InlineData("gen_ai.evaluation.explanation")]
public void GenAiProperties_AreNotTruncated_InRequestDataCustomDimensions(string propertyKey)
public void GenAiProperties_AreTruncatedTo256KB_InRequestDataCustomDimensions(string propertyKey)
{
// Arrange
using var activitySource = new ActivitySource(nameof(GenAiTruncationExemptionTests));
using var activitySource = new ActivitySource(nameof(GenAiTruncationTests));
using var activity = activitySource.StartActivity(
"TestActivity",
ActivityKind.Server,
Expand All @@ -244,8 +243,7 @@ public void GenAiProperties_AreNotTruncated_InRequestDataCustomDimensions(string

// Assert
Assert.True(requestData.Properties.TryGetValue(propertyKey, out var value), $"Property '{propertyKey}' should exist in request custom dimensions.");
Assert.Equal(LargePayloadLength, value!.Length);
Assert.Equal(s_largePayload, value);
Assert.Equal(SchemaConstants.GenAi_Properties_MaxValueLength, value!.Length);
}
}
}
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